I'm thinking a putting an outdoor fireplace into an outdoor kitchen design and making myself out of concrete block, firebrick and finishing it in stucco. I want to make sure that the fireplace draws well and going up 25 feet seems to ensure that this will work.

Is there a limit as to how high I can go simply stacking the concrete block and filling with cement and rebar? Can I go 25ft high or at some point is is just too much weight?

Personally, I wouldn't go higher than six feet with the dry stack method. It's not so much compression as lateral stability that would concern me. For what you're planning, I'd go for a traditional mortar joint from the ground up. Why 25 feet, by the way? You could get lots of draw at half that.

Just as a side note, the dry stack and fill method works with eight inch (full size) concrete blocks. Once you get up over the support slab, you don't need that much masonry surrounding your chimney. Four inch blocks are easier to lay up, lighter to lift, cheaper to buy, and all that code requires to surround your flue tile. They even make chimney blocks to make the job easier.

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